What exactly are the things that break the fast?

The boundary is set in the verse that also fixes the daily hours: “It has been made permissible for you the night preceding fasting to go to your wives for sexual relations. They are a clothing for you and you are a clothing for them. Allah knows that you used to deceive yourselves, so He accepted your repentance and forgave you. So now, have relations with them and seek that which Allah has decreed for you i.e., offspring. And eat and drink until the white thread of dawn becomes distinct to you from the black thread of night. Then complete the fast until the night i.e., sunset. And do not have relations with them as long as you are staying for worship in the mosques. These are the limits set by Allah, so do not approach them. Thus does Allah make clear His verses i.e., ordinances to the people that they may become righteous.” (Qur’an 2:187)

What breaks the fast without dispute:

1. Eating or drinking deliberately. 2. Sexual intercourse during the hours of the fast, which carries an expiation as well as making the day up. 3. Making yourself vomit. 4. Menstruation or post-natal bleeding, at any point in the day.

What does not break it:

• Eating having completely forgotten you were fasting.
• Rinsing, brushing your teeth, showering, swimming.
• Swallowing saliva, smelling food, tasting without swallowing.
• Waking in a state of major impurity.
• Involuntary vomiting, bleeding gums, a wound.

What is not settled: injections, inhalers, eye drops, patches, withdrawal of blood in quantity. The four schools were never asked about any of this, and different bodies have reached different conclusions. Anyone wanting certainty on one of them should ask a scholar of their own school.

The practical rule for a first Ramadan: if you did not intend it and it was not food, drink or intimacy, your fast is almost certainly fine.